Swash zone dynamics in a rythmic 'black-sand' beach system (1992)
AuthorsMarra, J. J.show all
Patterns of physical change and the processes regulating change in the swash zone were examined at Nine Mile Beach, a heavy mineral-rich sand beach located on the west coast of the South Island, New Zealand. Concurrent observations of process and response parameters were made across scales ranging spatially from meters to millimetres and temporally from days to seconds. These observations indicate that a multi-scale system of process-response interactions governs swash zone dynamics. At the macroscale, interactions between incident wave conditions and beach/surf zone morphologies define a process-response network. At the microscale, interactions between swash/backwash flow characteristics, bedforms, sedimentary structures and sediment textures define a process-response network. Interactions between wave runup characteristics, beach water table characteristics, foreshore morphology, and foreshore stratigraphy define a mesoscale process-response network. Interactions exist between, as well as within, each of these process-response networks. Specifically, a connection from incident wave condition-morphologic interactions occurring at the macroscale to flow-grain-bed interactions operating at the microscale, is established through their mutual relationship to the temporal and spatial variations in the relative dominance of swash versus backwash forces operating at the mesoscale. Thus, while each network of process-response interaction may be viewed in isolation, it is in conglomeration that they define the larger network of interactions that constitutes swash zone dynamics.